Leather finish



Patented May so, 1933 UNITED STATES Lanai? PATENT OFFICE EDWARD F.ARNOLD, OF NEW BRUNSWICK, NEW JERSEY, ASSIGNOR TO' E. I. DU PON'I DENEMOURS & COMPANY, OF WILMINGTON, DELAWARE, A CORPORATION OF DELAWARELEATHER FINISH No Drawing.

This invention relates to coating compositions, and to a new process oftreating leather. More particularly the invention relates to cellulosederivative coating compositions which when applied to a pliable basesheet, specifically leather, give a soft, pliable product having adecorative, water shedding finish of pleasing appearance.

Prior to my invention, the best method of surfacing leather was by meansof the socalled water finish. This consisted in applying an emulsion ofcertain materials, such as casein, oils and pigments, in water to thesurface of the leather, and in working it in. As is known, this processgives a soft, pliable product having a decorative finish of veryattractive appearance but it necessitates a very considerable time forapplication and an extremely long time for drying. The lastnameddisadvantage requires the use of a very large space for the drying ofthe finished leather. however, the water finish has, heretofore, givenbetter results than cellulose derivative finishes because cellulosederivative finishes, although applicable in very short periods of timeand although very quick to dry, have had the disadvantage of giving ahard, unpleasant appearance to the leather, and a surface hard and hornyto the touch, which upon boarding, wrinkles into large ridges, in whichcracks will form, the edges of which break free from the leather.

The boarding process referred to above is carried out by folding thefinished leather, grain side in, pressing upon the crease, and pullingthe upper fold of the leather past the lower fold while maintainingpressure upon the crease. Asthis is done the creased line moved acrossthe leather and produced a series of creases about I mm. apart. Byfolding the skin completely in one direction, and then in a direction atright angles to the first, a box grain pattern is produced. By foldingthe third time in a direction diagonal to the other two, a pebble effectis obtained. By boarding the fourth time in the other diagonal directionthat finish is produced which is known as morocco. Folding with old typecellulose derivative finishes gave an Despite this disadvantage,

Application filed January 31, 1930. Serial No. 4253153.

unsightly appearance, while with a water finish the excellent andfamiliar grained leathers resulted.

Among the objects of. this invention are to produce a coatingcomposition which, when applied to a pliable base sheet, specificallyleather, will have the advantage of both old types of finish and thedisadvantages of neither, and which, in addition, will render theleather washable. A further object of my invention is to produce acoating composition having excellent adhesion and low film stren th.

These objects are accomplished, generally speaking, by incorporating waxinto a cellulose derivative coating composition, and in applying thiscomposition to the surface to be protected.

In general the coating composition of my invention comprises a cellulosederivative, such as cellulose nitrate or cellulose acetate, Wax, asoftener, a solvent, and a diluent.

It is possible with my invention to entirely eliminate the use of aplasticizer. By grinding the wax and pigments together and thenincorporating this mixture in the film-forming ingredients the wax ismade to perform the function, usually performed by the plasticizer, ofincorporating the pigment into the composition. In grinding the wax andpigment, or ingrinding the wax alone for those compositions which are tocontain no pi ment, excellent results are'obtained by grin ing thestated ingredients in alcohol to give a milky suspension.

A general idea of the amounts of filmforming ingredients which may beused in the solids of the coating composition after decomposition on theleather, may be obtained by reference to the following illustrativeexample, the proportions of which are not to be deemed limitative:

. 7 Parts Nitrocellulose 10.0 Softener .0 to 10 Wax 1.0 to 40 Pigment ordye 0.0 to 4:0

This composition, in any indicated proportion of its ingredients, isapplied to a leather surface and is worked into the leather by anysuitable means. It is not essential that the composition be worked intothe leather, but

preferred results are obtained if this manipulation is carried out.

The following six examples give specific formulae which can besuccessfully used to accomplish the objects of my invention.

These examples are illustrative only and are not to be deemed in anysense limitative.

Example I Per cent High viscosity cellulose nitrate .7 Dibutyl phthalate.8 Carnauba Wax 1.7 Titanium oxide I 3.3 Ethyl acetate 15.5 Butylacetate 10.3 Ethyl alcohol 66.7

Example 1] Per cent High viscosity cellulose nitrate 1.7 Dibutylphthalate .8 Beeswax 1.7 Titanium oxide 3.3 Ethyl acetate 15.5 Butylacetate 10.3 Ethyl alcohol 66.7

Example [[1 Per cent High viscosity cellulose nitrate 1.7 Dibutylphthalate .8 (landelilla wax 1.7 Titanium oxide 3.3 Ethyl acetate 15.5Butyl acetate 10.3 Ethyl alcohol 66.7

Example IV Per cent Low viscosity cellulose nitrate Dibutyl phthalate2.5 Carnauba wax 5.0 Butyl acetate 30.0 Ethyl acetate 57.5

Example V Per cent Cellulose acetate .7 Dibutyl tartrate .8 (Jarnaubawax 1.7 Acetone 53.7 Alcohol 9.0 Diacetone alcohol 33.1

Example VI The compositions named above, and other compositions which Iuse in the practice of my invention, may be prepared by any of themethods useful in preparing cellulose derivative lacquers. Any knowntype of cellulose nitrate may be used whose use in plastics, films,lacquers, etc., is advantageous. The range of viscosity of cellulosenitrates which have been successfully used, is very Wide, cellulosenitrates when incorporated in a 16 oz. solution in GP ethyl acetatehaving viscosities between 50 centipoises and 25,000 centipoises,measured in the Stormer viscometer at 28 (3., having provedsatisfactory.

In place of cellulose nitrate any suitable cellulose ester, such ascellulose acetate, may be employed, but their use will be accompanied bya variation in the amounts of the solvents and softeners employed inorder to obtain the best composition. The proportions of diiferentingredients to be used depend upon the particular ingredients used, andno general rule for the incorporation can be given beyond what is hereinindicated.

The nature of the plasticizer in this composition is not important. Anycellulose ester plasticizer which is compatible with the remainder ofthe mixture and capable of dispersing the desired pigments can be used.Examples are dibutyl phthalate, castor oil, tricresyl phosphate anddibutyl tartrate. It is understood that these examples are illustrativeand not inclusive.

A particular advantage of my invention resides in the fact that bygrinding the wax and pigmenttogether the use of plasticizers can beentirely eliminated. This grinding of wax and pigment together isfacilitated by the presence of a substance such as alcohol.

The pigment to be used may consist of a single pigment or dye, or of acombination of pigments, or dyes, designed to give any desired coloreffect. Any pigment whose use in lacquers is suitable may be used withmy invention, or the pigment may be left out entirely and a clear finishbe utilized. Examples of pigments which I have successfully used arezinc oxide, titanium oxide, chrome yellow or orange, iron oxide and ironblue. An example of a useful dye is nigrosine.

The use of a high ratio of inert material to binder contributes to thediscontinuity of the film and can be used with advantage.

Pisang wax The waxma be of any kind, including those of vegeta 1eanimal, insect, mineral or synthetic origin. The following waxes areexam les of those which are more or less suit- 5 able or use in mycoating composition:

Carnauba wax Candelilla wax Montan wax 0 Beeswax Flax wax Raphia waxCotton seed wax Condang wax Sugar cane wax Insect (Chinese) wax Psyllawax Bayberry wax Cofi'ee berry wax Palm wax Japan wax Myrtle wax Ceresinwax Ocotilla wax Ozokerite wax It is advantageous to use a wax, such ascarnauba, candelilla, beeswax, Montan, having a melting point such thatit does not soften under the mechanical finishing operations and smearthe finish. Waxes having the higher melting points or softening pointshave been found to give excellent results under operating conditions.Carnauba wax appears to be particularly advantageous in this connection.

It is not generally desirable to use a'resin in my composition as mostresins tend to produce a sticky film when subjected to the mechanicaloperation of leather finishing. However, suitable natural, or synthetic,resins, such as shellac, can be successfully used when a finish of highgloss is desired.

Any of thehquids commonly used as solvents for the cellulose derivativesmay be used although it is advisable to adopt those which give the bestcompatibility, flow, blush resistance, etc.

It is advisable to dilute my coating compositions with a suitablequantity of alcohol or other thinner, the proportion of dilutiondepending upon the method of application,-

the physical characteristics of the sk'n to be finished, and the type offinish desired. In general a dilution of approximately twice the weightof the composition is satisfactory.

A coating composition of my invent'on may be applied by any of themethods known to the finishing of leather, such as by brushing,swabbing, roller coating, or spraying, although the latter methodbecause of its ease and speed is preferred. Any known method of applyinga uniform film of the coating composition to the base sheet may beemployed. -If the composition is to, be applied b swabbing, ahigh-boiling solvent should used. In the application of a coatingcomposition to a piece of leather, the leather may be stretched on aframe to obtain a smooth surface. The composition is then applied andforms a continuous film which will remain continuous as long as the skinis not moved or disturbed. However, when the skin is subjected tograining, or boarding, the 5 film breaks at all points where stress isapplied. This is due to the fact that the film strength is so weak thatwhen the leather carrying the finish is grained or boarded itimmediately cracks or breaks, forming, instead of unsightly ridges ofprior art pyroxylin coated leather, microscopic cracks similar to thoseproduced when a water finish is subjected to the same treatment. Thusthe coat ing, instead of being a continuous film completely covering theskin, presents a surface coated with discontinuous small patches oflacquer through which the ventilation so necessary to the wearerscomfort can take place when the leather is being used for shoes.

My invention is not to be confused with the cation. It is, furthermore,to be noticed that my composition differs distinctly from prior artcompositions in that it does not contain any more plasticizer than thesmall amount which serves to properly grind and incorporate the pigmentsin the composition. Indeed, the use of a considerable amount ofplasticizer is deleterious in that it requires the use of increasedamounts of wax and pigment to give my composition its desired fragility.'In fact as has been above indicated the plasticizer may be eliminated.

Although the principal use of my new coating composition is in finishingleather to obtain a soft, pliable product having a decorative, watershedding finish, my coating composition is also suitable to theproduction of artificial leather in which art it can be used either byapplying it to a fabric or other suitable base to produce a leather, orby application as a finishing material to artificial leathing or paperarticles, (such as containers and wallpaper), linoleum, wood, and othersurfaces. An instance of its utility is the fact that ink which has beendropped on wallpaper treated with my coating composition can be washedoff without the slightest injury to the paper or the finish.

Among the advantages of my invention over water finishes are case andspeed of application, rapid drying (which removes the necessity forlarge storage places), and relative freedom from smutting when wet.Among the advantages of my invention over previous cellulose derivativesare the lower cost which results from the practical elimination ofexpensive plasticizers, its good adhesion, and its beautiful appearanceand feel. Other advantages will be apparent to those skilled in the art.

As many apparently widely different embodiments of this invention may bemadewithout departing from the spiritand scope thereof, it is to beunderstood that I do not limit myself to the specific embodimentsthereof except as defined in the appended claims.

I claim:

1. A soft, pliable product having a decorative, water shedding finish,said product comprising a pliable base sheet carrying a substantiallyuniform surface film thereon including a cellulose derivative and a wax,said film having its continuity broken up by a plurality ofsubstantially microscopic cracks.

2. A soft, pliable product having a decorative, water shedding finish,said product comprising a pliable base sheet carrying a substantiallyuniform surface film thereon including cellulose nitrate and a wax, saidfilm having its continuity broken up by a plurality of substantiallymicroscopic cracks.

3. A soft, pliable product having a decorative, water shedding finish,said product comprising a pliable leather base sheet carrying asubstantially uniform surface film thereon including a cellulosederivative and a wax, said film having its continuity broken up by aplurality of substantially microscopic cracks.

4. A soft, pliable product having a decorative, Water shedding finish,said product comprising a pliable leather base sheet carrying asubstantially uniform surface film thereon including cellulose nitrateand a Wax, said film having its continuity broken up by a plurality ofsubstantially microscopic cracks.

5. A soft, pliable product having a decorative, water shedding finish,said product comprising a pliable leather base sheet carrying asubstantially uniform surface film thereon including cellulose nitrateand a wax selected from thegroup consisting of carnauba, candelilla,beeswax and Montan waxes, said film having its continuity broken up by aplurality of substantially microscopic cracks.

6. A soft, pliable product having a decorative, water shedding finish,said product comprising a pliable leather base sheet carrying asubstantially uniform surface film thereon including cellulose nitrateand carnauba wax, said film having its continuity broken up by aplurality of substantially microscopic cracks.

7. A soft, pliable product having a decorative, water shedding finish,said product comprising a pliable leather base sheet carrying asubstantially uniform surface film thereon including cellulose nitrate,a wax, and coloring matter, said film having its continuity broken .upby a plurality of substan tially microscopic cracks.

8. A soft, pliable product having. a decorative, water shedding finish,said product comprising a pliable leather base sheet carrying asubstantially uniform surface film thereon including cellulose nitrate,a wax, a plasticizer and a pigment, said film having its continuitybroken up by a plurality of substantially microscopic cracks.

9. A soft, pliable product comprising a pliable leather base sheetcarrying a substantially uniform surface film thereon having itscontinuity broken up by a plurality of substantially microscopic cracks,said film being obtained by coating a composition including cellulosenitrate, carnauba wax, dibutyl phthalate, a pigment, ethyl acetate,butyl acetate, and ethyl alcohol on said leather base sheet, and thensubjecting said base sheet to mechanical action whereby the continuityof the coated film is broken up by a plurality of substantiallymicroscopic cracks.

10. Method of preparing a soft, pliable sheet having a decorative, watershedding finish which comprises uniformly applying a compositionincluding a cellulose derivative and a wax to a pliable base sheet, andthen subjecting the sheet to mechanical action whereby the continuity ofthe film formed by said composition is broken up by a plurality ofsubstantially microscopic cracks.

11. Method of preparing a soft, pliable leather sheet having adecorative, water shedding finish which comprises uniformly applying acomposition including a cellulose derivative and a wax to a pliableleather base sheet, and then subjecting the sheet to mechanical actionwhereby the continuity of the film formed by said composition is brokenup by a plurality of substantially microscopic cracks.

12. Method of preparing a soft, pliable leather sheet having adecorative, water shedding finish which comprises uniformly applying acomposition including cellulose nitrate and a wax to a pliable leatherbase sheet, and then subjecting the sheet to mechanical action wherebythe continuity of the film formed by said composition is broken up by aplurality of substantially microscopic cracks.

In testimony whereof, I aflix my signature.

EDWARD F. ARNOLD.

